Field of the Invention
The present application relates to an optical receiver that converts a received optical signal into an electrical signal.
Related Background Art
Recent optical communication system installs optical receivers that convert optical signals transmitted through optical fibers with sensitivity. Such an optical receiver often implements a trans-impedance amplifier (TIA) in a front end thereof to amplify a faint signal converted from the received optical signal by a photodiode (hereafter denoted as PD).
Various techniques have been reported to enhance the dynamic range of a TIA. One technique installs a composite feedback element of a resistor and a diode connected in parallel to each other. A large input current automatically turns on the diode in the feedback element, which equivalently reduces the feedback impedance. Another prior art of a TIA provides a variable feedback resistor to vary, exactly reduce the closed feedback gain. However, such techniques are hard to secure the high frequency performance of the TIA. Also, a variable resistor implemented within the feedback element, which is typically a field effect transistor (FET), inevitably accompanies parasitic capacitance and degrades a small signal response of the TIA. One modification has been investigated to cope the response in a high input current with that in a small input current by raising an input DC level when the TIA receives the high input current. However, no TIA that fully satisfies the response for the small input current and that in the large input current without degrading temperature response of a TIA.